Buggy code:
public class ClassUtils { public static final char PACKAGE_SEPARATOR_CHAR = '.' ; public static final String PACKAGE_SEPARATOR = String . valueOf ( ClassUtils . PACKAGE_SEPARATOR_CHAR ) ; public static final char INNER_CLASS_SEPARATOR_CHAR = '$' ; public static final String INNER_CLASS_SEPARATOR = String . valueOf ( ClassUtils . INNER_CLASS_SEPARATOR_CHAR ) ; private static final Map < Class < ? > , Class < ? > > primitiveWrapperMap = new HashMap < Class < ? > , Class < ? > > ( ) ; private static final Map < Class < ? > , Class < ? > > wrapperPrimitiveMap = new HashMap < Class < ? > , Class < ? > > ( ) ; private static final Map < String , String > abbreviationMap = new HashMap < String , String > ( ) ; private static final Map < String , String > reverseAbbreviationMap = new HashMap < String , String > ( ) ; private static void addAbbreviation ( String primitive , String abbreviation ) { } public ClassUtils ( ) { } public static String getShortClassName ( Object object , String valueIfNull ) { } public static String getShortClassName ( Class < ? > cls ) { } public static String getShortClassName ( String className ) { } public static String getPackageName ( Object object , String valueIfNull ) { } public static String getPackageName ( Class < ? > cls ) { } public static String getPackageName ( String className ) { } public static List < Class < ? > > getAllSuperclasses ( Class < ? > cls ) { } public static List < Class < ? > > getAllInterfaces ( Class < ? > cls ) { } public static List < Class < ? > > convertClassNamesToClasses ( List < String > classNames ) { } public static List < String > convertClassesToClassNames ( List < Class < ? > > classes ) { } public static boolean isAssignable ( Class < ? > [ ] classArray , Class < ? > [ ] toClassArray ) { } public static boolean isAssignable ( Class < ? > [ ] classArray , Class < ? > [ ] toClassArray , boolean autoboxing ) { } public static boolean isAssignable ( Class < ? > cls , Class < ? > toClass ) { } public static boolean isAssignable ( Class < ? > cls , Class < ? > toClass , boolean autoboxing ) { } public static Class < ? > primitiveToWrapper ( Class < ? > cls ) { } public static Class < ? > [ ] primitivesToWrappers ( Class < ? > [ ] classes ) { } public static Class < ? > wrapperToPrimitive ( Class < ? > cls ) { } public static Class < ? > [ ] wrappersToPrimitives ( Class < ? > [ ] classes ) { } public static boolean isInnerClass ( Class < ? > cls ) { } public static Class < ? > getClass ( ClassLoader classLoader , String className , boolean initialize ) throws ClassNotFoundException { } public static Class < ? > getClass ( ClassLoader classLoader , String className ) throws ClassNotFoundException { } public static Class < ? > getClass ( String className ) throws ClassNotFoundException { } public static Class < ? > getClass ( String className , boolean initialize ) throws ClassNotFoundException { } public static Method getPublicMethod ( Class < ? > cls , String methodName , Class < ? > [ ] parameterTypes ) throws NoSuchMethodException , SecurityException { } private static String toCanonicalName ( String className ) { className = StringUtils . deleteWhitespace ( className ) ; if ( className == null ) { <START_BUG> throw new NullArgumentException ( "className" ) ; <END_BUG> } else if ( className . endsWith ( "[]" ) ) { StringBuffer classNameBuffer = new StringBuffer ( ) ; while ( className . endsWith ( "[]" ) ) { className = className . substring ( 0 , ( ( className . length ( ) ) - 2 ) ) ; classNameBuffer . append ( "[" ) ; } String abbreviation = ClassUtils . abbreviationMap . get ( className ) ; if ( abbreviation != null ) { classNameBuffer . append ( abbreviation ) ; } else { classNameBuffer . append ( "L" ) . append ( className ) . append ( ";" ) ; } className = classNameBuffer . toString ( ) ; } return className ; } public static Class < ? > [ ] toClass ( Object [ ] array ) { } public static String getShortCanonicalName ( Object object , String valueIfNull ) { } public static String getShortCanonicalName ( Class < ? > cls ) { } public static String getShortCanonicalName ( String canonicalName ) { } public static String getPackageCanonicalName ( Object object , String valueIfNull ) { } public static String getPackageCanonicalName ( Class < ? > cls ) { } public static String getPackageCanonicalName ( String canonicalName ) { } private static String getCanonicalName ( String className ) { } }

Fix:
throw new NullPointerException ( "className<seq2seq4repair_space>must<seq2seq4repair_space>not<seq2seq4repair_space>be<seq2seq4repair_space>null." ) ;